1. Field of the Invention
The present invention relates to a three-dimensional (hereinafter, referred to as “3D”) shape measuring system for measuring the 3D shape of a measurement object.
2. Description of the Background Art
There has been conventionally known a noncontact 3D shape measuring device for measuring fragmentary 3D shapes of a measurement object in a noncontact manner at a plurality of measurement positions around the measurement object whose shape is to be measured and measuring the overall 3D shape of the measurement object based on these measurement results. The following patent literatures are, for example, known to disclose a technique of measuring the 3D shape of a shape measurement object.
Japanese Patent Unexamined Publication No. 2001-201325 discloses a technique of synthesizing a plurality of partial images for the purpose of obtaining a clear two-dimensional (hereinafter, referred to as “2D”) image having the focus adjusted to the entire object to be observed (micro-object). Here, the plurality of partial images are obtained by performing an operation of specifying a part within the depth of focus of the object to be observed from interference fringes of a 2D interferometer, extracting the image of this part and storing this image in a memory a plurality of times.
Japanese Patent Unexamined Publication No. H07-160893 discloses a technique of obtaining 3D information by successively obtaining edge images of an object from time-series images picked up by photographing the same object by a camera from different viewpoints, and estimating a moved amount of the camera this time based on the 3D information of the object restored up to the last time and the edge images of the object at the present point in time.
In a technique disclosed in Japanese Patent No. 3501359, an image of an object is picked up a plurality of times while the focus position is cyclically moved. Then, the process of extracting focused pixels (in-focus pixels) from the respective images is performed for the last cycle, and the extracted in-focus image for the last cycle are synthesized. This synthesized image is displayed on a liquid crystal monitor.
Japanese Patent Examined Publication No. H06-58212 discloses a technique of picking up an image of a measurement object a multiple of times while changing an in-focus position, determining focused images for parts of the measurement object from a multitude of obtained images, and obtaining three-dimensional coordinates 3D coordinates of the respective parts.
In the conventional 3D shape measurement of the measurement object, an operator had to judge whether or not any unmeasured area exists on the measurement object outside the present measurement range. Further, if the operator judges the presence of the unmeasured area outside the present measurement range, it was difficult to properly set a destination of the measurement range (moving amount and moving direction) in order to perform a measuring operation at the next measurement position.
In order to avoid this, it can be thought to perform the measuring operation by setting a moving pitch of the measurement range beforehand and moving the measurement range at the set moving pitches within a specified area regardless of 3D shape of the measurement object. However, there are cases where the measurement range is moved and the measuring operation is performed despite the absence of the unmeasured area outside the present measurement range, thereby causing occurrences of unnecessary operations and prolonging the measurement. It should be noted that a technique of automatically determining the destination of the measurement range for the measuring operation at the next measurement position is disclosed in none of the above four patent literatures.